An electric double layer capacitor is quickly chargeable and dischargeable, tough against over-charge&discharge, long in life for cause of no chemical reaction, workable under wide range of temperature, and easy on the environment for cause of heavy metal free, and has other property which battery does not have. An electric double layer capacitor is mainly employed for a memory backup power supply and so on. An electric double layer capacitor is researched in application to electric power storing system or engine assist for hybrid car by assembling with battery such as solar battery and fuel cell.
An electric double layer capacitor comprises a pair of polarizable electrodes comprising a laminate of a collector such as an aluminum foil and a composition containing an activated carbon, in which the pair of polarizable electrodes set facing each other in solution containing electrolytic ion, and a separator is interposed between the polarizable electrodes. Impressing of direct current voltage into the electrodes causes drawing anion in solution to cathode (positive electrode) and drawing cation in solution to anode (negative electrode), making an electric double layer at the interface between electrode and solution. And the electric double layer can supply electric energy.
An internal resistance of an electric double layer capacitor needs to be as low as possible in order to obtain an electric double layer capacitor having high output and high capacity. It is known that an internal resistance of a capacitor is caused from an electrolytic solution, a polarizable electrode, a collector, and interface between them. So attempt to lower an internal resistance of the capacitor by lowering a volume resistance of the collector or the electrode has been carried out.
Patent document 1 discloses an electrode for an electric double layer capacitor comprising a laminate of an aluminum foil having a thickness of 10 to 50 μm, a conductive layer having a thickness of 0.2 to 20 μm and an electrode layer having a thickness of 80 to 500 μm in turn. The conductive layer is made from a conductive coating material comprising a graphite powder as a conductive material and polyamide-imide resin as a binder.
[Patent Document 1] JP-2002-270470-A
Patent document 2 discloses an electrode for an electric double layer capacitor comprising a laminate of an electrode layer containing a carbon material having a specific surface area of 100 to 2500 m2/g and a high conductive layer which is porous and has an electric conductivity higher than that of the above electrode layer in turn, in which the electrode layer is on a collector for an electrode. There is described that the electrode layer containing a carbon material having a specific surface area of 100 to 2500 m2/g is pasted on the collector for an electrode by using a conductive adhesive containing carbon.
[Patent Document 2] JP-2003-309045-A
Patent document 3 discloses a collector for an electric double layer capacitor comprising: a film comprising a conductive material and thermoplastic resin, and a tow electric resistance layer being on the film.
[Patent Document 3] JP-2004-31468-A